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POIs JIT reason of this behaviour?
 

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  1. POIs JIT reason of this behaviour?
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    <p>Inspired by this <a href="https://stackoverflow.com/questions/18460580/is-the-check-thread-safe">question</a>, I wrote the test:</p> <pre><code>public class Main { private static final long TEST_NUMBERS = 5L; private static final long ITERATION_NUMBER = 100000L; private static long value; public static void main(final String [] args) throws Throwable { for(int i=0; i&lt;TEST_NUMBERS; i++) { value = 0; final Thread incrementor = new Thread(new Incrementor()); final Thread checker = new Thread(new Checker()); incrementer.start(); checker.start(); checker.join(); incrementer.join(); } } static class Incrementor implements Runnable { public void run() { for(int i=0; i&lt;ITERATION_NUMBER; i++){ ++value; } } } static class Checker implements Runnable { public void run() { long nonEqualsCount = 0; for(int i=0; i&lt;ITERATION_NUMBER; i++){ if(value != value) { ++nonEqualsCount; } } System.out.println("nonEqualsCount = " + nonEqualsCount); } } } </code></pre> <p>This program are printed in common case:</p> <pre><code>nonEqualsCount = 12; //or other non 0 value; nonEqualsCount = 0; nonEqualsCount = 0; nonEqualsCount = 0; nonEqualsCount = 0; </code></pre> <p>First: I explain this behaviour is presence of the JIT-compiler. JIT-compiler cache value non <code>volatile</code> field for each thread after "warmup". It right?</p> <p>Second: If first right or not right, how can I verify this?</p> <p>P.S. - I know about <strong>PrintAssebly</strong>-option.</p> <p><strong>Update:</strong> enviroment: Windows 7 64bit, JDK 1.7.0_40-b43(Hot Spot).</p>
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    1. USSergey Morozov
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    1. COtry with public void safePrintln(String s) { synchronized (System.out) { System.out.println(s); } }
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    2. CO@barn.gumbl: System.out is synchronized. See (PrintStream)[http://grepcode.com/file/repository.grepcode.com/java/root/jdk/openjdk/7-b147/java/io/PrintStream.java?av=f]
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      1. USAaron Digulla
 

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